There are two shapes of boar frozen semen production, and the results of these two shapes of frozen semen in experimental or extension, the delivery rate and litter size of granular and straw frozen semen were 56% vs. 59% and 8.5 vs. 8.6 respectively (Johnson, 1985). The results of the Porcine Research Institute (PRI) were 56% vs. 63% delivery rate and 7.8 vs. 8.1 litters per litter (Kuo, You-Hai and Yang, 1992). There was no significant difference in fertility between the two shapes of frozen semen. However, the method of thawing frozen semen in wheat tubes is simpler and less contaminated, and it is easily accepted by pig breeders. Therefore, the frozen semen produced by the Institute of Swine Research is based on the McTubular type of frozen semen.

The process of making frozen semen in wheat tubes and the thawing process are briefly described as follows:

＊The process of making frozen semen in wheat tubes for boars:

1. Collection of semen (150 ml in the thick part of semen)

2. Microscopic examination of sperm motility (at 200X magnification) and sperm morphology (at 800X magnification)

3. Dilute the semen with Modena diluent

4. Cool the diluted semen to 15°C (4 hours)

5. Separate the diluted semen telecentrically (800g) at 15°C for 10 minutes at room temperature

6. Discard the supernatant

7. Dilute the semen with Egg Yolk Lactose diluent

8. 9. Dilute the semen with egg yolk lactose diluent containing 6% glycerol

10. Fill 6 ml wheat tubes with 5 ml of diluted semen

11. Place the wheat tubes on a flat rack in a polytron box containing liquid nitrogen and freeze for 20 minutes

12. Transfer the frozen wheat tubes into a liquid nitrogen tank for storage

Thawing of frozen semen in wheat tubes:

1. Remove the frozen semen from the liquid nitrogen tank as soon as possible

2. Place the wheat tubes in a bath of warm water at 50°C for 45 seconds

3. Wipe off the surface of the wheat tubes and cut one end of the tubes

4. Cut the other end of the tubes to allow the semen to flow into the 80 ml of diluent at 25°C

5.

5. Use phase contrast microscope to check the character of thawed semen

6. Inseminate the thawed frozen semen as soon as possible

The number of doses of frozen semen produced by the Institute of Swine Research (ISSR) since 1975*** are four types of Blue Rhee

(L) 1271 doses, Yorkshire

(Y) 1040 doses, Duroc

(D) 2114 doses and the number of doses for the Durham

(D) 2114 doses, and the number of doses of the Durham

(D) 2114 doses. p> (D) 2114 doses and Hambrosia

(H) 37 doses (Guo Youhai and Jiang Rongzhang, 1997).

The average farrowing rate and litter size of boar frozen semen inseminated sows tested or promoted by the Institute of Porcine Research (IPR) in the past years were 59.4% (706/1188) and 8.7 litters (including pellet and wheat tube frozen semen), which showed that the difference in the farrowing rate of frozen semen compared with that of fresh semen was about 20%, and the number of litters was about 2.0 head less.

So how to close the gap between frozen and fresh semen? The global research boar frozen semen experts to pursue the dream, perhaps in the near future can really come true, although the process of making frozen semen on the pig sperm damage, coupled with its sensitivity to cold shock is also very high, not only damage to the sperm in the freezing process, and on the life of living sperm is also with the shortening of the sperm, but if you can seize the time of the sow's ovulation with the frozen semen, then, the results should not be too bad. According to the report of Dr. Weberski (1994), a German reproduction expert, the most suitable time for insemination with frozen semen is 4 hours before the sow ovulates, and such a practice can get a satisfactory fertilization rate (88.1%). Therefore, how to determine when the sow ovulates is a major factor in the performance of frozen semen insemination in sows.